Spectrophotometric determination of ascorbic acid by using bismuth containing 18-molybdodiphosphate

Abstract

Reactions of formation and reduction of bismuth substituted 18-molybdophosphate (18-MBPC) with ascorbic acid (Asc) have been investigated. 18-MBPC is reduced by Asc in the presence of Bi(III) ions at the ratio of Asc:18-MBPC 1:1 and 2:1 with formation of, respectively, two- and four-electron reduced heteropoly blues. Their spectra are similar to the spectra of metalsubstituted heteropoly blues with Keggin structure and have an absorption maximum at 690 nm. Selective, rapid and simple method was developed for the determination of Asc. Benefits of using the 18-MPBC as analytical reagent are high sensitivity and rate of reduction rate, including the behavior in acid solutions. The limit of detection was of 2.6·10–6mol/l (l = 1 cm), and ε was of 1.15·104mol–1·l·cm–1.